In some instances of prior networks, a single protocol with a defined modulation technique has been used to provide communications among various network nodes. In such exemplary networks, each node generally may be configured to comply with a specific set of characteristics that make it interoperable with the other nodes of the network.
In order to transmit information among network nodes, RF packets may be sent from one node to another. Such packets generally may typically be considered to include two parts: a synchronization header and a payload that contains the data to be sent. The synchronization header is typically used to make the receiver aware that a packet is arriving and such as to let the receiver make adjustments to properly receive the data. In certain exemplary simple implementations, a synchronization header may be made up of a preamble and a synchronization word, sometimes referred to as a start of frame delimiter. For purposes of the present disclosure, the term “preamble detection” may be considered and used interchangeably with the term “synchronization header detection.”
In certain of previously known networks, the receiving process can be detailed as several steps, some of them being optional, but generally including steps to detect the presence of the packet, distinguish the packet from noise or interference to avoid false alarms, recover the carrier frequency, recover the data rate, adjust the amplifier gain according to the incoming packet power, and synchronize the receiver for the reception of the first data symbol.
As a particular network evolves over time, it may be subject to occurring that new nodes can be added that are equipped with newer (or otherwise different) generation RF hardware. Such newly added nodes in some instances may be able to communicate using more sophisticated modulation techniques and protocols, resulting for example in better performance and/or data throughput. On the other hand, it's desirable that such exemplary new devices be able to communicate with the older (or preexisting) devices in order to be sure of the overall connectivity of the network. Such situations naturally (or inherently) lead to the coexistence of two or more different modulation techniques being used (or needed) over the same network. It would be advantageous, therefore, to be able to manage or otherwise handle such coexistence situations without otherwise impairing the global network performance.
Additionally, in many real-life network implementations, some nodes will have a relatively more difficult time joining the network. In certain instances, such nodes may tend to be located far away from the other nodes, thereby contributing to their inability or difficulty in joining the network. Alternatively, such nodes may be located in a basement, a shielded cabinet, or other area that may tend to attenuate RF signals. In such exemplary cases, such signal attenuation may prevent the nodes from joining the network, or may make it more difficult.
Radio links in general are known to be able to support a relatively large dynamic range, allowing communication with close neighbor nodes as well as with more relatively remote nodes. However, in a relatively larger network, some nodes may tend to nearly always be out-of-reach. One technique for addressing issues resulting in such communication problems is to use an adaptive modulation technique that adapts the data rate according to the communication link quality. Under such technique, a lower bit rate may be used to communicate with those nodes that suffer from poor link quality. Such technique can be integrated into a single protocol that uses the lowest data rate for the synchronization header and then adapts the payload data rate according to the situation per a handshake mechanism. Such techniques are known to be practiced in modem and RF technology, but such approach generally has some limitations when relatively very large data rate variations need to be spanned.
The following patent documents are examples of prior publications relating to various aspects of communications: U.S. Pat. No. 7,953,190 by Patel et al., entitled “Parallel preamble search architectures and methods;” U.S. Pat. No. 7,460,621 by Lewis, entitled “Detection;” US Application Publication No. 2011/0110229 by Himayat et al., entitled “Multi-radio communication between wireless devices;” US Application Publication No. 2011/0044395 by Hansen et al., entitled “Mixed mode preamble for MIMO wireless communications;” US Application Publication No. 2009/0310699 by Kodama et al., entitled “Communication apparatus, communication method, and integrated circuit;” and US Application Publication No. 2007/0155423 by Carmody et al., entitled “Multiprotocol wireless communication backbone.” The complete disclosures of the herein referenced patent related publications are fully incorporated herein for all purposes.
Generally it can be beneficial to use a specific modulation scheme dedicated to low quality links, but such practices in general may again tend to bring about a problem of operating a wireless network with completely different modulation techniques. It would be generally advantageous, therefore, to develop a system where multiple protocols may be employed in harmony with each other to provide communications among variously located nodes within a network.